feat(edit): pick a location from the contact picker

Reuse the attendee contact-picker mechanism for the location field: a
Contacts button beside the location input opens the system picker scoped
to postal-address rows, and the chosen contact's formatted address is
dropped into the field (multi-line addresses collapsed to one line).

Same no-permission guarantee as the guest picker — ACTION_PICK grants
temporary read access, so no READ_CONTACTS is required.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src/main/res/values/strings.xml

@@ -82,6 +82,7 @@
     <string name="event_edit_add_guest">Add guest</string>
     <string name="event_edit_add_guest_hint">Add a guest by email…</string>
     <string name="event_edit_add_guest_from_contacts">Add from contacts</string>
+    <string name="event_edit_location_from_contacts">Pick address from contacts</string>
     <string name="event_edit_remove_guest">Remove guest</string>
     <string name="event_edit_attendee_required">Required</string>
     <string name="event_edit_attendee_optional">Optional</string>